This invention relates generally to a catalyst system for the polymerization of olefins, more specifically, to the prepolymerization of supported catalyst systems and the use thereof
Supported metallocene catalyst systems are used primarily in slurry, bulk liquid, and gas-phase polymerization processes. In general the catalyst systems and various methods to make them from transition metal components and activators are well known and exploited. These supported catalyst systems may be subjected to a prepolymerization step to enhance performance. Prepolymerization often confers the advantages of reduced fines formation, and superior product properties such as better granular morphology, higher bulk density, and improved granule flow properties. See EPA 447,071.
EPA 279,863 discloses a method for preparing a supported, prepolymerized metallocene catalyst system. The specific metallocene used is Cp2ZrCl2 which is supported on silica and prepolymerized with ethylene. EPA 279,863 suggests using a molecular weight controlling agent such as hydrogen to produce a prepolymer having certain intrinsic viscosities. Applicants have found that certain low activity catalyst systems containing certain metallocenes such as Cp2ZrCl2 may be supported and prepolymerized without fouling the prepolymerization reactor and without producing agglomerated catalyst particles.
However, other catlyst systems, such as high activity catalyst systems tend to foul the prepolymerization reactor and/or produce agglomerated catalyst system particles. It would be highly desirable to have an efficient method for using such catalyst systems without fouling and agglomeration in the prepolymerization reactor.
This invention relates to a method for yielding a non-fouling, non-agglomerating supported prepolymerized catalyst system. The invention involves use of hydrogen to control the fouling and agglomeration observed during prepolymerization of high activity supported catalyst systems which tend to foul during prepolymerization.
The invention relates to a method for controlling fouling in a prepolymerization reactor, said method comprising the step of combining:
(a) a supported metallocene catalyst system having an activity greater than about 100,000 g/g/hr.;
(b) at least one alpha olefin monomer feed; and,
(c) added hydrogen
under suitable prepolymerization reaction conditions. Ethylene and/or propylene are used as the preferred monomer feed for the prepolymerization of these supported catalysts.
Preferably, the metallocene catalyst system of this invention has a known tendency to foul a prepolymerization reactor and/or produce agglomerated catalyst system particles upon prepolymerization. Even more preferably, the metallocene catalyst system has an activity of from about 100,000 g polymer/g metallocene/hr to about 1,000,000 g polymer/g metallocene/hr. preferably greater than 150,000 g polymer/g metallocene/hr., even more preferably greater than 200,000 g polymer/g metallocene/hr. or from about 150,000 g polymer/g metallocene/hr to about 900,000 g polymer /g metallocene/hr., preferably from about 200,000 g polymer /g metallocene/hr to about 500,000 g polymer/g metallocene/hr.
Hydrogen is generally added in an amount of from about 0.1 to about 10 mole percent relative to the monomer feed rate. The monomer feed is generally added at a rate of about 0.1 to about 10 g olefin/g catalyst solid/hour. Suitable prepolymerization reaction conditions are typically run at low temperatures, for example in the range of from about xe2x88x9220xc2x0 C. to about 40xc2x0 C., preferably from about xe2x88x9210xc2x0 C. to about 20xc2x0 C., most preferably from about 0xc2x0 C. to about 10xc2x0 C.
Still further, the invention relates to use of the prepolymerized catalyst system formed by the method described herein and further relates to a method for controlling agglomermation of catalyst particles during the prepolymerization procedure.
Prepolymerization reactor fouling and catalyst agglomeration which are observed during the prepolymerization of some metallocene catalyst systems, particularly high activity metallocene catalyst systems, can be minimized or eliminated by the use of hydrogen during prepolymerization. In a preferred embodiment, a supported metallocene catalyst system having high activity, monomer feed containing at least one alpha olefin, and added hydrogen are combined in a prepolymerization reactor, under suitable prepolymerization reaction conditions to control fouling and agglomeration of the supported catalyst system during prepolymerization. A further embodiment of the invention relates to the use of the prepolymerized supported catalyst system prepared by the method described herein for the polymerization of olefins to polyolefins.
For purposes of this application and claims, the phrase xe2x80x9cadded hydrogenxe2x80x9d is defined to mean hydrogen which is purposely added during the prepolymerization reaction. Hydrogen which may be generated in-situ is excluded from this definition. Fouling is defined occurs when material sticks to the walls of the reactor. Agglomeration occurs when the catalyst system particles stick to each other. Fouling and agglomeration may or may not occur together.
As used herein, xe2x80x9cmetallocenexe2x80x9d and xe2x80x9cmetallocene catalyst componentxe2x80x9d mean those bulky ligand transition metal compounds represented by the formula:
CpmMRnXq
wherein Cp is a cyclopentadienyl ring or derivative thereof, M is a Group 4, 5,or 6 transition metal and/or a metal from the lanthanide or actinide series, R is a hydrocarbyl group or hydrocarboxy group having from 1 to 20 carbon atoms, X is a halogen, and m=1-3, n=0-3, q=0-3, and the sum of m+n+q is equal to the oxidation state of the transition metal. The metallocene may be bridged or unbridged, and include heteroatoms in the structure. In addition, one or more bulky ligands may be xcfx84-bonded to the transition metal atom. Other ligands may be bonded to the transition metal, for example, a leaving group, such as but not limited to hydrocarbyl, hydrogen or any other univalent anionic ligand. Non-limiting examples of metallocenes and metallocene catalyst systems are discussed in for example, U.S. Pat. Nos. 4,530,914, 4,952,716, 5,124,418, 4,808,561, 4,897,455, 5,278,264, 5,278,119, 5,304,614 all of which are herein fully incorporated by reference. Also, the disclosures of EP-A-0 129 368, EP-A-0 591 756, EP-A-0 520 732, EP-A-0 420 436, WO 91/04257 WO 92/00333, WO 93/08221, and WO 93/08199 are all fully incorporated herein by reference. The preferred transition metal component of the catalyst system of the invention are those of Group 4, particularly, zirconium, titanium and hafnium. The transition metal may be in any oxidation state, preferably +3 or +4 or a mixture thereof.
Preferred metallocenes comprise a Group 4, 5, or 6 transition metal, biscyclopentadienyl derivatives, preferably bridged bis-indenyl metallocene components having the following general structure: 
wherein M1 is a metal of Group 4, 5, or 6 of the Periodic Table, for example titanium, zirconium, hafnium, vanadium niobium, tantalum, chromium, molybdenum and tungsten, preferably, zirconium, hafnium and titanium, most preferably zirconium;
R1 and R2 are identical or different, are one of a hydrogen atom, a C1-C10 alkyl group, preferably a C1-C3 alkyl group, a C1-C10 alkoxy group, preferably a C1-C3 alkoxy group, a C6-C10 aryl group, preferably a C6-C8 aryl group, a C6-C10 aryloxy group, preferably a C6-C8 aryloxy group, a C2-C10 alkenyl group, preferably a C2-C4 alkenyl group, a C7-C40 arylalkyl group, preferably a C7-C10 arylalkyl group, a C7-C40 alkylaryl group, preferably a C7-C12 alkylaryl group, a C8-C40 arylalkenyl group, preferably a C8-C12 arylalkenyl group, or a halogen atom, preferably chlorine;
R3 and R4 are hydrogen atoms;
R5 and R6 are identical or different, preferably identical, are one of a halogen atom, preferably a fluorine, chlorine or bromine atom, a C1-C10 alkyl group, preferably a C1-C4 alkyl group, which may be halogenated, a C6-C10 aryl group, which may be halogenated, preferably a C6-C8 aryl group, a C2-C10 alkenyl group, preferably a C2-C4 alkenyl group, a C7-C40-arylalkyl group, preferably a C7-C10 arylalkyl group, a C7-C40 alkylaryl group, preferably a C7-C12 alkylaryl group, a C8-C40 arylalkenyl group, preferably a C-8-C12 arylalkenyl group, a xe2x80x94NR215, xe2x80x94SR15, xe2x80x94OR15, xe2x80x94OSiR315 or xe2x80x94PR215 radical, wherein R15 is one of a halogen atom, preferably a chlorine atom, a C1-C10 alkyl group, preferably a C1-C3 alkyl group, or a C6-C10 aryl group, preferably a C6-C9 aryl group; 
xe2x95x90BR11 , xe2x95x90AlR11, xe2x80x94Gexe2x80x94, xe2x80x94Snxe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x95x90SO, xe2x95x90SO2, xe2x95x90NR11, xe2x95x90CO, PR11, or xe2x95x90P(O)R11;
wherein:
R11, R12 and R13 are identical or different and are a hydrogen atom, a halogen atom, a C1-C20 alkyl group, preferably a C1-C10 alkyl group, a C1-C20 fluoroalkyl group, preferably a C1-C10 fluoroalkyl group, a C6-C30 aryl group, preferably a C6-C20 aryl group, a C6-C30 fluoroaryl group, preferably a C6-C20 fluoroaryl group, a C1-C20 alkoxy group, preferably a C1-C10 alkoxy group, a C2-C20 alkenyl group, preferably a C2-C10 alkenyl group, a C7-C40 arylalkyl group, preferably a C7-C20 arylalkyl group, a C8-C40 arylalkenyl group, preferably a C8-C22 arylalkenyl group, a C7-C40 alkylaryl group, preferably a C7-C20 alkylaryl group or R11 and R12, or R11 and R13, together with the atoms binding them, can form ring systems;
M2 is silicon, germanium or tin, preferably silicon or germanium, most preferably silicon;
R8 and R9 are identical or different and have the meanings stated for R11;
m and n are identical or different and are zero, 1 or 2, preferably zero or 1, m plus n being zero, 1 or 2, preferably zero or 1; and
the radicals R10 are identical or different and have the meanings stated for R11, R12 and R13. Two adjacent R10 radicals can be joined together to form a ring system, preferably a ring system containing from about 4-6 carbon atoms.
Alkyl refers to straight or branched chain substituents. Halogen (halogenated) is fluorine, chlorine, bromine or iodine atoms, preferably fluorine or chlorine.
Particularly preferred metallocenes are compounds of the structures: 
wherein:
M1 is Zr or Hf, R1 and R2 are methyl or chlorine, and R5, R6 R8, R9, R10, R11 and R12 have the above-mentioned meanings.
The chiral metallocenes are used as a racemate for the preparation of highly isotactic polypropylene copolymers.
It is also possible to use either the pure R or S form. An optically active polymer can be prepared with these pure stereoisomeric forms. It is preferred that the meso form of the metallocenes be removed to ensure the center (i.e., the metal atom) provides stereoregular polymerization.
Separation of the stereoisomers can be accomplished by known literature techniques. For special products it is also possible to use rac/meso mixtures.
Generally, the metallocenes are prepared by a multi-step process involving repeated deprotonations/metallations of the aromatic ligands and introduction of the bridge and the central atom by their halogen derivatives. The following reaction scheme illustrates this generic approach: 
The reader is referred to the Journal of Organometallic Chem., volume 288 (1958), pages 63-67, and EP-A-320762, for preparation of the metallocenes described, both references are herein fully incorporated by reference.
Illustrative but non-limiting examples of metallocenes include:
Dimethylsilandiylbis(2-methyl-4-phenyl-1-indenyl)ZrCl2 
Dimethylsilandiylbis(2-methyl-4,5-benzoindenyl)ZrCl2;
Dimethylsilandiylbis(2-methyl-4,6-diisopropylindenyl)ZrCl2;
Dimethylsilandiylbis(2-ethyl-4-phenyl-1-indenyl)ZrCl2;
Dimethylsilandiylbis(4-naphthyl-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-4-phenyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-(1-naphthyl)-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-(2-naphthyl)-1-indenyl)ZrCl2,
Dimethylsilandiylbis(indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4,5-diisopropyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2,4,6-trimethyl-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl2,
1,2-Ethandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl2,
1,2-Butandiylbis(2-methyl-4,6-diisopropyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-t-butyl-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-4-isopropyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-ethyl-4-methyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2,4-dimethyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4-ethyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-a-acenaphth-1-indenyl)ZrCl2,
Phenyl(M(ethyl)silandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-4,5-(methylbenzo)-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-4,5-(tetramethylbenzo)-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-xcex1-acenaphth-1-indenyl)ZrCl2,
1,2-Ethandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl2,
1,2-Butandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-4,5-benzo-1-indenyl)ZrCl2,
1,2-Ethandiylbis(2,4,7-trimethyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-1-indenyl)ZrCl2,
1,2-Ethandiylbis(2-methyl-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-1-indenyl)ZrCl2,
Diphenylsilandiylbis(2-methyl-1-indenyl)ZrCl2,
1,2-Butandiylbis(2-methyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-ethyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl2,
Phenyl(Methyl)silandiylbis(2-methyl-5-isobutyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2-methyl-5-t-butyl-1-indenyl)ZrCl2,
Dimethylsilandiylbis(2,5,6-trimethyl-1-indenyl)ZrCl2, and the like.
The preferred metallocene catalyst components of this invention are described in detail in U.S. Pat. Nos. 5,149,819, 5,243,001, 5,239,022, 5,296,434 arid 5,276,208 all of which are herein fully incorporated by reference. Also preferred are those catalysts described in U.S. Pat. No. 5,296,434 herein fully incorporated by reference.
The metallocenes discussed above are activated to form the active catalyst system or xe2x80x9cmetallocene catalyst system.xe2x80x9d The metallocene activator may be any compound or component which can activate a bulky ligand transition metal compound or a metallocene as defined above. Alumoxane may be used as the activator as well as ionizing activators, neutral or ionic. For example, compounds such as tri(n-butyl)ammonium bis(pentaflurophenyl)boron, which ionize the neutral metallocene compound, may be used as the activator. Examples of ionizing activators and methods of their production and use may be found in U.S. Pat. Nos. 5,153,157; 5,198,401; 5,241,025; 5,278,119; and 5,384,299 herein fully incorportated by reference.
Alumoxane is represented by the formula: Rxe2x80x94(Al(R)xe2x80x94O)nxe2x80x94AlR2 for oligomeric linear alumoxanes and (xe2x80x94Al(R)xe2x80x94Oxe2x80x94)m for oligomeric cyclic alumoxane wherein n and m are 1 to 40, preferably 3 to 20, and R is a C1-8 alkyl group or R is an C6-18 aryl group, or hydrogen, preferably a methyl group, or R can be mixtures of alkyl and aryl substituents. Alumoxane or methylalumoxane can be prepared by a variety of known processes such as those illustrated in, for example, U.S. Pat. Nos. 4,665,208; 4,952,540; 5,091,352; 5,206,199; 5,204,419; 4,874,734; 4,924,018; 4,908,463; 4,968,827; 5,308,815; 5,329,032; 5,248,801; 5,235,081; 5,157,137; and 5,103,031 (each incorporated herein by reference).
Descriptions of ionic catalysts for coordination polymerization comprised of metallocene cations activated by non-coordinating anions appear in the early work in EP-A-0 277 003, EP-A-0 277 004 and U.S. Pat. No. 5,198,401 and WO-A-92/00333 (each incorporated herein by reference). These teach a preferred method of preparation wherein metallocenes (bisCp and monoCp) are protonated by an anionic precursors such that an alkyl/hydride group is abstracted from a transition metal to make it both cationic and charge-balanced by the non-coordinating anion.
The term xe2x80x9cnoncoordinating anionxe2x80x9d means an anion which either does not coordinate to said cation or which is only weakly coordinated to said cation thereby remaining sufficiently labile to be displaced by a neutral Lewis base. xe2x80x9cCompatiblexe2x80x9d noncoordinating anions are those which are not degraded to neutrality when the initially formed complex decomposes. Further, the anion will not transfer an anionic substituent or fragment to the cation so as to cause it to form a neutral four coordinate metallocene compound and a neutral by-product from the anion. Noncoordinating anions useful in accordance with this invention are those which are compatible, stabilize the metallocene cation in the sense of balancing its ionic charge in a +1 state, yet retain sufficient lability to permit displacement by an ethylenically or acetylenically unsaturated monomer during polymerization. Additionally, the anions useful in this invention will be large or bulky in the sense of sufficient molecular size to largely inhibit or prevent neutralization of the metallocene cation by Lewis bases other than the polymerizable monomers that may be present in the polymerizaton process. Typically the anion will have a molecular size of greater than or equal to about 4 angstroms.
The use of ionizing ionic compounds not containing an active proton but capable of producing the both the active metallocene cation and an noncoordinating anion is also known. See, EP-A-0 426 637 and EP-A-0 573 403 (incorporated herein by reference). An additional method of making the ionic catalysts uses ionizing anionic pre-cursors which are initially neutral Lewis acids but form the cation and anion upon ionizing reaction with the metallocene compounds, for example the use of tris(pentafluorophenyl) boron. See EP-A-0 520 732 (incorporated herein by reference). Ionic catalysts for addition polymerization can also be prepared by oxidation of the metal centers of transition metal compounds by anionic pre-cursors containing metallic oxidizing groups along with the anion groups, see EP-A-0 495 375 (incorporated herein by reference).
Where the metal ligands include halogen moieties (for example, bis-cyclopentadienyl zirconium dichloride) which are not capable of ionizing abstraction under standard conditions, they can be converted via known alkylation reactions with organometallic compounds such as lithium or aluminum hydrides or alkyls, alkylalumoxanes, Grignard reagents, etc. See EP-A-0 500 944 and EP-A1-0 570 982 for in situ processes describing the reaction of alkyl aluminum compounds with dihalo-substituted metallocene compounds prior to or with the addition of activating anionic compounds.
Methods of supporting ionic catalysts comprising metallocene cations and noncoordinating anions are described in WO91/09882, WO 94/03506 and in co-pending U.S. Ser. No. 08/248,284, filed Aug. 3 1994 (each incorporated herein by reference). The methods generally comprise either physical adsorption on traditional polymeric or inorganic supports that have been largely dehydrated and dehydroxylated, or using neutral anion precursors that are sufficiently strong Lewis acids to activate retained hydroxy groups in silica containing inorganic oxide supports such that the Lewis acid becomes covalently bound and the hydrogen of the hydroxy group is available to protonate the metallocene compounds.
Typically, the support can be any organic or inorganic, inert solid, particularly, porous supports such as talc, inorganic oxides, and resinous support materials such as polyolefin. Suitable inorganic oxide materials that are desirably employed include Groups-2a, -3a, -4a, -4b, or -5b metal oxides such as silica, alumina, silica-alumina, and mixtures thereof. Other inorganic oxides that may be employed either alone or in combination with the silica, alumina, or silica-alumina are magnesia, titania, zirconia, and the like. Other suitable support materials can be employed such as, finely divided polyolefins, such as polyethylene.
Other examples of inorganic supports or carriers include SiO2, Al2O3, MgO, ZrO2, TiO2, Fe2O3, B2O3, ZnO, ThO2, and mixtures thereof such as silica-alumina, zeolite, ferrite, and glass fibers.
Generally, activation is carried out in a solution containing dissolved activator. When alumoxane is used as the activator the concentration, of alumoxane in the solution may range from about 1% by weight up to the saturation limit, preferably, from about 5% to about 30% by weight in each case based on the entire solution. The metallocene is dissolved in this solution such that the concentration of metallocene in solution may be up to the saturation limit. Preferably the atomic ratio of the alumoxane aluminum atom to the metallocene metal atom is from about 1 to about 1000, preferably about 10 to about 700, more preferably about 100 to about 400. The time required for activation may be from about 5 minutes or more, preferably from about 5 to about 60 minutes at a temperature ranging from about xe2x88x9278xc2x0 C. to about 100xc2x0 C., preferably from about 0xc2x0 C. to about 40xc2x0 C.
Alternatively, ionic activators may be used as described above in which case the activation may be carried out in solution at a temperature ranging from about xe2x88x92100xc2x0 C. to about 300xc2x0 C., preferably from about 0xc2x0 C. to about 100xc2x0 C. The time for reaction may range from about 10 seconds to about 60 minutes depending upon variables such as reaction temperature and choice of reactants.
The prepolymer formed during the prepolymerization may be a homopolymer or copolymer. If a copolymer is desired, monomer mixtures, such as ethylene-propylene, ethylene-butene or ethylene-hexene mixtures may be introduced into the prepolymerization reactor. Generally, the prepolymer is made up of one or more alpha olefins having between 2 and about 20 carbon atoms. Preferably the principle olefin contains between 2 and about 10 carbon atoms, most preferably 2 or 3 carbon atoms.
In a preferred embodiment, the hydrogen is generally added in an amount between about 0.1 to about 10 mole percent relative to the monomer feed rate under prepolymerization conditions. Hydrogen is preferably added at about 0.5 to about 6 mole percent and most preferably from about 1 to about 3 mole percent relative to the monomer feed rate.
In a preferred embodiment the olefin feed or monomer is polymerized onto the supported, solid, catalyst system thereby forming the prepolymer during the prepolymerization reaction. The olefin feed is preferably added during prepolymerization at a rate of from about 0.1 to about 10 g olefin/g catalyst solid/hour, more preferably from about 0.1 to about 5 g olefin/g catalyst solid/hour, and most preferably at a rate of from about 0.5 to about 1.5 g olefin/g catalyst solid/hour. Prepolymer contents of from about 0.05 to about 30 g prepolymer/g catalyst is an acceptable and general amount formed during the prepolymerization reaction. Preferably an amount of from about 0.1 to about 20 g prepolymer/g catalyst is formed, and most preferably an amount in the range of about 0.2 to about 10 g prepolymer/g catalyst is formed onto the supported catalyst system during the prepolymerization process.
Experiments for this invention were generally run with a calculated prepolymerization rate of about 0.5 to about 1.0 g prepolymer/g catalyst/hour using ethylene as the monomer. This rate resulted in no fouling or agglomeration of the prepolymerized supported catalyst system. Additionally, the prepolymerized catalyst had a granular morphology and was free flowing.
Preferred prepolymerization reaction conditions generally include low temperatures, for example, in the range of about xe2x88x9220 to about 40xc2x0 C. Preferably the temperature during prepolymerization is in the range of about xe2x88x9210 to about 20xc2x0 C. and most preferably is in the range of about 0 to about 10xc2x0 C. Solvents suitable for use during the prepolymerization include inert hydrocarbons such as isopentane, hexane, and the like. A solvent is generally chosen so as it does not interact with the supported catalyst system. The reaction time is dependent upon the amount of prepolymer being formed on the catalyst.
In an embodiment of the invention, the supported catalyst system is a metallocene-alumoxane catalyst system supported on silica in accordance with the support technique described in U.S. Pat. No. 5,240,894, incorporated by reference. The support technique described in U.S. Pat. No. ""894 involves production of a metallocene-alumoxane reaction product which is then placed on dehydrated silica and thoroughly dried prior to use. In an alternate embodiment, the catalyst system may be supported in accordance with that taught in U.S. Pat. Nos. 4,937,301 or 5,008,228 which involves adding the metallocene, and trimethylaluminum to a water impregnated or wet silica support. In a further alternate embodiment the catalyst may be supported in accordance with U.S. Pat. No. 4,808,561 which describes placing the metallocene on a methylalumoxane coated silica support. Any support technique generally useful for producing catalyst for use in gas phase or slurry polymerization is acceptable for the purposes of this invention. For example, support techniques described in U.S. Pat. Nos. 4,808,561; 4,897,455; 4,937,301; 4,937,217; 4,912,075; 5,008,228; 5,086,025; 5,147,949; and 5,240,894 may be employed, all references incorporated by reference. The examples herein describe supporting a catalyst in accordance with the techniques described in U.S. Pat. Nos. 5,240,894; 4,937,301; 4,808,561. The examples of the invention illustrate that the invention works well with a variety of techniques.
The invention is further illustrated by the following non limiting examples. All solvents were purchased from commercial sources, nitrogen purged and dried over activated molecular sieves. Unsubstituted Cp2ZrCl2 was purchased from commercial sources. Alumoxane solutions were purchased as 10-30 wt % solutions. Silica is Davison 948 (average particle=50 microns) dehydrated at either 200 or 800xc2x0 C. under flow of nitrogen.